1. Field of the Invention
The invention relates to a method of covering energy peak demands in electrical alternating or three-phase current networks and to a circuit arrangement for covering peak energy demand in electrical alternating or three-phase current networks. A stand-by power supply is generally realized by a DC network fed from accumulators.
2. Description of the Prior Art
It is already known that the large electricity utilities have to reserve at least 2.5% of the total produced power as a so-called primary regulating reserve in order to make a quickly activatable, non-reactive, power reserve available in electricity supply systems.
This normally takes place by thermal producing units by means of the turbine operating mode "controlled flexi-pressure". In this way, up to 5% of the nominal power can be kept available as a primary regulating reserve with the required dynamic properties.
This manner of operation leads, however, on the one hand, to efficiency penalties. On the other hand, producer units with cost-favorable primary energy costs are not operated at their nominal power in order to keep available the 5% primary regulating reserve. Together they lead to extra cost in making electrical energy available.
Furthermore, it is known to use stand-by power supplies with rectifiers in electric stores for the stand-by power supply of, for example, driving voltage systems, telecommunication systems, interruption-free installation, such as, for example, computers, special emergency power supplies, for example, in operating theaters in hospitals, safety lighting systems, generating stations, substations, communication centers, hospitals, large buildings in general etc. The industrial accumulators or batteries used for this purpose generally have a working life of 10 to 20 years. However, they are only used about 50 times during their entire working life including the test periods. Such known stand-by power supplies are thus also ultimately un-economical because of the lack of use of the expensive electrochemical energy stores.
Finally, accumulator-based, auxiliary power stations are also known which are provided exclusively with accumulators and the charging devices required for them, of which the accumulators are charged up in low demand periods via rectifiers and which feed electrical energy into the attached network via inverters when a higher demand is present. These accumulator-based, auxiliary power stations are comparable with pumped storage power stations. They have to be made available specially to deliver the peak demand and otherwise have no function.